The present invention relates to a window function for an aperture and more specifically to a Bragg cell spectral analyzer wherein a window function is provided for apodization of diffraction at an aperture of the cell.
The dynamics of a Bragg cell spectral analyzer in the environment of a signal is limited by the diffraction of the laser beam at the finite aperture of the Bragg cell and can be reduced by apodization with suitable window functions.
Many such window functions which enable an apodization of the secondary diffraction maximums under a specific target level, particularly under a target level of -50 dB under the level of the principal diffraction maximum, are described in the literature (v. F. J. Harris, "On the Use of Windows for Harmonic Analysis with the Descrete Fourier Transform", Proc. IEEE 66 (1978) 51-83 and P. Jacquinot, B. Roizen-Dossier, Apodization, Progress in Optics III, E. Wolf, ed., North-Holland Publ. Comp., Amsterdam, 1964), incorporated herein by reference. But a more or less pronounced spread of the principal diffraction maximum is always connected therewith. This means a deterioration of the frequency resolution and thus of the dynamics for the Bragg cell spectral analyzer.